In a number of fluid delivery processes, a flow passage is required to sequentially receive n fluids one after another from the 1st fluid to the nth fluid and to repeat the process endlessly in a progressive and cyclic manner. If multiple flow passages are required to go through the same process simultaneously, as in the case of the simulated moving bed chromatography, the operation is very complex and a special fluid diverting device is needed.
U.S. Pat. No. 3,706,812 describes a rotary valve for this process. The rotary valve comprises three basic parts: a stationary disc, a rotating disc, and a stationary collar ring. The lower face of the stationary disc and the upper face of the rotating disc are in close contact to form a first leak-proof seal and the interior of the stationary collar ring and the exterior of the rotating disc are in close contact to form a second leak-proof seal. The stationary disc has inlet ports on its upper face and circular grooves concentrically spaced apart on its lower face, each inlet port is in communication with one corresponding circular groove. The rotating disc has radial flow passages with inlet openings on the upper face and the outlet openings spacing apart equally on the exterior. The stationary collar ring has outlet ports and each outlet port is in communication with one of the outlet openings of the flow passages of the rotating disc. The inlet openings of the rotating disc locate at different radial distances from the axis of the rotating disc and the radial distances correspond to the radius of the respective circular grooves so that each inlet opening of the rotating disc is always connected with a corresponding circular groove of the stationary disc as the rotating disc rotates. In this way, a fluid will flow in the valve from the same path in the stator and the rotator (from an inlet port, through a concentric groove, an inlet opening, a flow passage, to a outlet opening) but is diverted into different outlet ports of the stationary collar ring. Multiple fluids can be diverted to different outlet ports in a simultaneous, progressive, and cyclic manner by stepwise turning the rotating disc of the rotary valve.
Currently the rotary valve of the prior art is primarily used for fluid-diversion in the applications of low pressure and fewer fluid-paths. For high pressure and more fluid-paths applications, other fluid-diversion means have to be used. This is due to the inherent limitation of the prior art. In the prior art, the circular grooves are concentrically arranged on the lower face of the stationary disc and their number determines the number of flow paths of the rotary valve. The addition of a circular groove to the rotary valve means an exponential increase of the disc size, the rotor-stator contacting area, and the fluid contacting area due to the concentric arrangement of these circular grooves. The increase of the disc size results in a large-sized valve that is inconvenient. The increase of the rotor-stator contacting area means a significant increase of friction that prevents the rotary valve from rotation. The increase of fluid contact area generates a larger force that pushes the stator disc apart from the rotator disc and impairs the seal between the stator disc and the rotator disc when the fluid has a high pressure. All these factors restrict the rotary valve of the prior art to a limited number of flow paths (usually four flow paths) and to the applications of low fluid pressures. Another drawback of the prior art is the relative large volume of the circular grooves and the dramatic volume differences among the circular grooves. These grooves trap the previous fluids and mix them with newly diverted fluids as contaminants by a stepwise rotation. The larger volume in these circular grooves means heavier contamination and the larger volume differences among these grooves means less precision, which should be minimized or avoided.
There is a need to have a new rotary valve for diverting multiple flows in a simultaneous, progressive, and cyclic manner. The rotary valve should be easily sealed and should withstand high pressures. The rotary valve should have minimal volumes in the circular grooves and the volumes of the circular grooves should be similar. The rotary valve should contain more flow paths for complicated applications.